Connecting a rheostat to a motor

Thread Starter


Joined Apr 2, 2017
I have a small squirrel cage fan that the motor has a capacitor on it. I'm trying to control the speed with a rheostat (dimmer switch). When connected, it is either off or full blast no matter what position it is in. Can I disconnect the capacitor or am I stuck with full speed all the time?



Joined Jan 15, 2015
The speed of the motor you have is proportional to line frequency. Note how the name plate data mentions 50/60 Hz and reflects two speeds associated with the two line frequencies. A dimmer switch will not vary the speed of that type motor. Motors that are line frequency dependent can have their speed varied by changing the line frequency, the devices used to do this are called a VFD (Variable Frequency Drive) and VFDs are not common to small squirrel cage motors. The motor you have was never intended to be run at speeds other than those on the name plate data.